The invention refers to a process for eliminating thermal interference for infrared and video-based early fire detection in waste incineration plants, recycling facilities, warehouses and the like, via a detection system that detects heat sources being coupled to a processing unit.
A process for processing noise signals of a noise source, e.g. of a traveling vehicle, of a workshop, is known from US 2004/0081322 A1. By performing a sound analysis of the signal features of detected noise signals and, as a result of this, using the determination of parameters of the noise source causing the noise signals, it is possible to document the temporal and/or spatial behaviors of the noise source. Thermal radiation is not addressed here.
Different sensor systems are known that can detect a fire. Furthermore, there are various extinguishing systems, i.e. fire extinguishing systems, with which fires are extinguished in industrial plants or larger rooms. Typically, a fire is detected and a fire extinguishing system is switched on, thereby spraying a large amount of extinguishing agent such as water or foam, in the fire area, flooding and thus extinguishes the fire. Of greatest importance is the detection of a fire. This takes place in particular by means of thermal differential detectors, smoke fire detectors, aspirating smoke detectors, flame detectors, infrared detectors and infrared cameras.
In particular sprinkler systems, which are significantly more powerful deluge facilities and manually controlled fire monitors can be used as extinguishing systems. The latter are referred to as cannons or as a water throwers.
Increasingly, more and more infrared detectors, in particular infrared cameras and video cameras, have been used for early fire detection in waste incineration plants, recycling plants, warehouses and the like.
Fire detection with fire detection systems based on infrared cameras is triggered when a limit temperature has been exceeded.
With video-based systems, fire detection is triggered by smoke detection, flame detection or by evaluating the short-wave infrared portion.
For example, in a warehouse, loaded with recycled materials, a temperature threshold of 80° C. as a fire alarm temperature is often defined as fire triggering temperature. The temperature is the one selected to be high so as not to detect self-heating by fermentation processes in the recycled material as a fire trigger. On the other hand, the alarm temperature is selected to be as low as possible in order to detect fires as soon as possible, which are located inside a material heap, or its rising convection heat that penetrates the surface of the material pile.
This method has proven itself and functions smoothly as long as there are no thermal interferences. These are generated for example by a hot exhaust or hot engine of a wheel loader. In operation, peak temperatures up to 500° C. can be achieved here quickly.
Currently, it has been attempted to eliminate these thermal interferences by using temperature and magnitude ratios. For example, the surface of an exhaust pipe of a wheel loader with a temperature limit of 80° C. quickly reaches a limit temperature exceeding area of 1 m2. This means that currently at least an area of 1 m2 must be detected above 80° C., to trigger a fire alarm. In everyday use, this area can even be increased. Consequently, the surface of the hot engine and the heated body parts near the engine is thus added to the exhaust area. It is also possible that juxtaposed wheel loaders and other vehicles combine to increase the size of disruptive areas. Since the distances between the infrared detection system and the vehicles vary, a tolerance must be factored in when determining the size of the limit temperature exceeding area. Ultimately, as soon the limit temperature exceeding area rises to 3 m2.
The advantage of early detection by infrared and video analysis is considerably weakened because such a large contiguous area that exceeds 80° C. in an aggregate material, requires a huge fire in said aggregate material. Also, a second higher limit temperature, for example at 200° C., does not change the result significantly. The smaller detection surface works in combination with a higher limit temperature, but again has the disadvantage that a concealed fire already has a significant size in an aggregate material.
Analysis now relate to the color, shape and markings to be able to identify the interferences clearly and include the considerable soil load of the objects and the fact that hot interfering objects such as an exhaust of vehicles, which are driven from the rain in a hall, behave exactly at a thermal image analysis as an initial fire whose temperature limit exceeding borders expand.
Furthermore, a distinction is made between the so-called “Day mode”, when vehicles may run within the area to be monitored for fire, and “Night mode”, when vehicles and other thermal interference sources such as thermal drive motors of machinery are not authorized.